The present invention relates to a data recording technique for a PCM data recorder utilizing a rotary head mechanism and, particularly, to a method and apparatus for recording PCM data suitable for arranging appended information associated with the PCM data in a recording medium without increasing the redundancy of the PCM data.
A PCM audio recording and reproducing system, which converts an analog audio signal into PCM digital signals, records the digital signals on a recording medium, and thereafter reproduces the digital signals and converts them back into the analog audio signal, achieves a drastic improvement in the reproduced sound quality as compared with the conventional analog audio recording and reproducing system. However, this system needs an amount of information to be transmitted which is approximately 50 times as much as the case of the analog audio system, and when a magnetic tape is used as the recording medium, it is necessary to increase the amount of information transmitted in a unit time length by increasing the number of tracks or by increasing the tape speed as practiced in the rotary head tape recorder system. Currently known PCM recording and reproducing (recorder) systems include a stationary-head type digital audio tape (S-DAT) recorder system using multiple tracks, and a rotary-head type digital audio tape (R-DAT) recorder system. The R-DAT system has great potential for the growth of PCM audio recorders among home users from the viewpoints of cost reduction, running economy and versatility of available functions. One of the functions which is practicable for the R-DAT system, but is not feasible for the S-DAT system is a fast address search function in a high-speed mode. This function appends a specific address code to each block of PCM data recorded on the tape, so as to indicate the block position among several music programs in a normal playback mode and also to search for a specific block of a record in the fast address search mode. In the R-DAT system, PCM signals are partitioned or divided into units of a certain number of symbols or words (e.g. one symbol consists of 8 bits), e.g., into 12-symbol units to essentially form a block, so that each block forms a unit number of symbols. A certain number of blocks, e.g., 128 blocks, are recorded on one track of the tape to form one frame, i.e., one track for a unit of PCM signal processing. See, for example, an article by Odaka "A Rotary Head High Density Digital Audio Tape Recorder" in the Institute of Electronics and Communication Engineers of Japan Electroacoustic Conference Data EA82-46 (1982).
FIG. 1 shows a record format of one block in a R-DAT system, also called a block format. The format includes a synchronizing signal 1 providing a reference timing in a playback operation, control signals 2 including information necessary to reproduce recorded PCM signals, PCM signals 3, and a parity signal 4 for error detection and correction. See, for example, a literature of Iwashita "Activity in DAD conference" in Japanese periodical "Electronics" published by EIAJ, October, 1984.
FIG. 2 shows, as an example, the detailed format of the control signals 2 shown in FIG. 1. In the control signal format, a 1-bit signal 5 is provided to identify the head or beginning of music programs recorded on the tape, by taking two signal levels "0" during a program, and "1" between adjacent programs, and this signal 5 is used to search for a program. PCM signal control information 6 associated with the recorded PCM signals includes the sampling frequency, the number of quantization bits, the quantization mode (linear, non-linear, etc.), analog characteristics (emphasis, noise reduction, etc.), a dubbing inhibit code, a mute signal, and the signal type. Recording of this information in BCD code would need as many as 24 bits. Track identification signal 7 is used to detect the occurrence of track-jump during a tape playkback operation, and it needs as many as 4 bits. Block address 8 is a signal for preventing the interleave-displacement during the playback operation, and it needs at least 7 bits for the case of recording 128 blocks in one track.
As described above, control signals need a total of about 36 bits, which is equal to almost 40% of each block PCM signal (12 symbols consist of 96 bits), thus increasing the bit redundancy.